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J. ASK.

Dentists Chair.

Patented Sept. 4, 1860.

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1.1 III! H UNITED snares PATENT OFFICE.

JUSTUS ASK, OF LYONS, NEW YORK, ASSIGNOR TO JAMES H. CASE, OF SAME PLACE.

CONSTRUCTION OF DENTAL CHAIRS.

Specification of Letters Patent No.

To all whom it may concern:

Be it known that I, J USTUS ASK, of Lyons, in the county of WVayne and State of New York, have invented a new and Improved Dental Chair; and I do hereby declare that the following is a full and exact description, reference being had to the accompanying drawings, in which,

Figure 1, is a vertical longitudinal section through the chair and footstool. Fig. 2, is a front view of the working parts and the front of the frame B, the seat and back being broken away to afford a better view. Fig. 3, is an inverted plan view of the working devices of the footstool.

Similar letters designate corresponding parts in all of the figures.

The general parts of my improved chair may be distinguished as follows. The frame or legs A, the seat frame B, back C, elevat ing seat D, and footstool E. The elevation of the seat D, is effect-ed by means of a stationary screw F, firmly attached to the bottom of the seat by bolts or screws a, a, and the loose revolving nut-wheel G. This nutwheel is supported by an annular seat in a strong iron frame (Z, securely fastened to the seat-frame B, by four arms 6, b, eXtend ing from the annular portion to the back and front of said frame. A cross bar or yoke 0, c, is attached to the sides of the annular frame above the nut-wheel, and prevents its rising with the screw. A stud e, from the frame (Z, forms one of the bearings of the crank shaft 7, to which is attached the beveled pinion it, which works into the beveled gear of the nut wheel. By turning the crank g, the revolutions of the wheel Gr, cause the screw to rise or fall, and consequently elevate or lower the seat D, according to the direction in which the crank is turned.

The seatD, has no guides, but is held steady in its position by the screw alone, which is prevented from vibrating laterally by the long hub or nut of the wheel. G, and by the broad surface which it presents to the annular seat on which it rests, and by the yoke c, which holds its top in place.

The seat frame B, is hinged to the legportion A, at each side about midway between the front and back which is made arching to admit of its being inclined back more or less, as required for the purposes for which it is used. The mechanism by which this is effected consists first of an in- 29,936, dated September 4, 1860.

verted bail K, which is hinged or pivoted to the forward arms 6, b, which attach the annular frame to the seat frame B. This bail can swing forward or back on its pivots j, j, and at the center of its bow or lower extremity, it is pivoted to the foot lever J, at or about the center thereof or to the arched piece t, which forms a portion of said lever. This pivot 2', being at right angles to those which attach the bail to its support, the two admit of free motion in two directions, sidewise, and forward and back; and this freedom of motion is important in order that the movable portion of the chair shall not become constrained, and thereby interfere with its operation in other respects. The lever J, has a foot piece Z, at one end, near which it passes through a guide slot in the piece M, which slot has a rack on one side into which the lug 0, (shown in Fig. 1) catches, the lever being pressed against the rack by a flat spring p, on the opposite side. The opposite end of the lever has its fulcrum on a pin 7", which passes through a slot '5, in the end of the lever, which also passes through a slot in the guide piece which holds the pin. This slot in the arm of the lever, admits of lts sliding on the pin as it is moved to raise and lower the seat, in order to not interfere with the free actions of the seat, but to leave all the mechanism of this part of the chair free to act around the two centers of motion, the pivots i and j, j, in the bail. The operator can thus with his foot adjust the inclination of the seat without leaving his position.

A flexible diaphragm R, formed like a bel-.

lows, unites the seat with the frame B, which from its form adapts itself to the contrac tion and expansion of the space between the two, as the seat is lowered or raised, thereby concealing the opening, and presenting an agreeable finish to the eye.

The movable seat is provided with supplementary arms S, Fig. 1, which, when the seat is down, fit the inner form of the permanent arms T, and serve as cushions thereto, but which being fixed to the seat, rise with it, and always remain at the same height above its surface. As the seat is often raised as high as the top of the arms T, it is important for the safety of children, as well as the comfort of adults, that there should be barriers at the sides, which want is fully supplied by the supplementary arms S, Without complicating the mechanism of K, arranged and operating substantially as the chair or impairing its symmetry.

What I claim as my invention and desire to secure by Letters Patent, is-- 1. The combination of the fixed screw F, nut-Wheel G, and its appurtenances, movable seat D, and frame A arranged and operating substantially in the manner and for the purposes shown and described.

2. The arched supporting frame A, with the seat-frame B, hinged thereto, in combination With the adjusting lever J, and bail and for the purposes set forth.

3. The supplementary seat-arms S, sub- 15 stantially as and for the purposes described.

4:- The bellovvs-formed diaphragm R, in combination With the movable seat and frame B, substantially as set forth.

J USTUS ASK.

Witnesses: S. J. ALLIs, J. H. CASE. 

